Buggy code:
public class Parser { private static final String EXCEPTION_NOTITLE = "no<seq2seq4repair_space>title<seq2seq4repair_space>inputed" ; private static final String EXCEPTION_INDEXILLEGAL = "the<seq2seq4repair_space>index<seq2seq4repair_space>you<seq2seq4repair_space>entered<seq2seq4repair_space>is<seq2seq4repair_space>illegal" ; private static final String EXCEPTION_NOINDEX = "you<seq2seq4repair_space>must<seq2seq4repair_space>enter<seq2seq4repair_space>an<seq2seq4repair_space>index" ; private static final String EXCEPTION_NULLPOINTER = "The<seq2seq4repair_space>command<seq2seq4repair_space>is<seq2seq4repair_space>null" ; private static final String FEEDBACK_ADD = "Tip:<seq2seq4repair_space>add<task><seq2seq4repair_space>-d<time><seq2seq4repair_space>-v<venue><seq2seq4repair_space>to<seq2seq4repair_space>add<seq2seq4repair_space>task<seq2seq4repair_space>with<seq2seq4repair_space>date<seq2seq4repair_space>&<seq2seq4repair_space>venue" ; private static final String FEEDBACK_DELETE = "Tip:<seq2seq4repair_space>delete<index><seq2seq4repair_space>to<seq2seq4repair_space>delete<seq2seq4repair_space>a<seq2seq4repair_space>task" ; private static final String FEEDBACK_MODIFY = "Tip:<seq2seq4repair_space>modify<index><seq2seq4repair_space><new<seq2seq4repair_space>title><seq2seq4repair_space>-d<new<seq2seq4repair_space>time><seq2seq4repair_space>-v<new<seq2seq4repair_space>venue><seq2seq4repair_space>to<seq2seq4repair_space>modify<seq2seq4repair_space>task" ; private static final String FEEDBACK_SORT = "Tip:<seq2seq4repair_space>sort<time//venue//title><seq2seq4repair_space>to<seq2seq4repair_space>sort<seq2seq4repair_space>tasks" ; private static final String FEEDBACK_SEARCH = "Tip:<seq2seq4repair_space>search<title//time//venue><seq2seq4repair_space>to<seq2seq4repair_space>search<seq2seq4repair_space>tasks" ; private static final String FEEDBACK_COMPLETE = "Tip:<seq2seq4repair_space>complete<index><seq2seq4repair_space>to<seq2seq4repair_space>mark<seq2seq4repair_space>a<seq2seq4repair_space>task<seq2seq4repair_space>completed" ; private static final int LARGE_CONSTANT = 500 ; private static final int FAIL = - 1 ; public enum Operation { UNKNOW , ADD , DELETE , CLEAR , DISPLAY , EXIT , MODIFY , UNDO , REDO , SORT , SEARCH , COMPLETE ; } private static final String [ ] KEYWORD_ADD = new String [ ] { "add" , "insert" } ; private static final String [ ] KEYWORD_DELETE = new String [ ] { "delete" , "remove" , "rm" } ; private static final String [ ] KEYWORD_CLEAR = new String [ ] { "clear" , "claen" } ; private static final String [ ] KEYWORD_DISPLAY = new String [ ] { "display" , "ls" , "show" } ; private static final String [ ] KEYWORD_EXIT = new String [ ] { "exit" , "quit" } ; private static final String [ ] KEYWORD_MODIFY = new String [ ] { "modify" , "update" } ; private static final String [ ] KEYWORD_UNDO = new String [ ] { "undo" } ; private static final String [ ] KEYWORD_REDO = new String [ ] { "redo" } ; private static final String [ ] KEYWORD_SORT = new String [ ] { "sort" } ; private static final String [ ] KEYWORD_SEARCH = new String [ ] { "find" , "search" } ; private static final String [ ] KEYWORD_COMPLETE = new String [ ] { "finish" , "complete" } ; private static final String [ ] OPTIONS = new String [ ] { "-v" , "-d" , "-dd" , "-c" } ; private static final Pattern NUMBERS = Pattern . compile ( ".*[^0-9].*" ) ; private static Hashtable < String , Parser . Operation > featureList = null ; private static DateParser dateParser = null ; private static String name = Parser . class . getName ( ) ; private static Logger logger = Logger . getLogger ( Parser . name ) ; public Parser ( ) { } public Parser . Operation getOperation ( String operation ) throws NullPointerException { } public boolean isValid ( String operation ) throws NullPointerException { } public boolean isArgumentsCorrect ( String operation ) throws NullPointerException { } public int getIndex ( String operation ) throws IOException { } public String getNewTitle ( String operation ) throws IOException , NullPointerException { } public String getTitle ( String operation ) throws IOException , NullPointerException { } public String getVenue ( String operation ) throws NullPointerException { if ( operation == null ) { logNullPointer ( Parser . EXCEPTION_NULLPOINTER ) ; } <START_BUG> return eliminateSpace ( getContent ( "-v" , operation ) ) ; <END_BUG> } public Date getDate ( String operation ) throws IOException , NullPointerException { } public Date getDeadline ( String operation ) throws IOException , NullPointerException { } public String autoFill ( String str ) throws NullPointerException { } public String privideTips ( String operation ) throws NullPointerException { } private String eliminateSpace ( String str ) { } private ArrayList < String > searchAllKeyword ( String str ) { } private String searchKeyword ( String str , String [ ] keyword ) { } private boolean isArgumentsTypeCorrect ( String operation ) { } private boolean isArgumentsNumberCorrect ( String operation ) { } private int countOptions ( String operationType , String operation ) { } private Parser . Operation getOperationIndex ( String operation ) { } private String combineString ( String [ ] temps ) { } private int getFirstOptionIndex ( String operation ) { } private void initFeatureList ( ) { } private void addSelectedFeature ( String [ ] keyword , Parser . Operation operation ) { } private String getContent ( String operationType , String operation ) { } private boolean isInOptions ( String operationType ) { } private int findType ( String operationType , String operation ) { } private void logNullPointer ( String msg ) throws NullPointerException { } private void logIOException ( String msg ) throws IOException { } }

Fix:
return getContent ( "-v" , operation ) ;